1. Field of the Invention
The invention relates to the telecommunications Common Channel Signaling (CCS) network particularly with respect to an applications platform therefor.
2. Description of the Prior Art
Telephone systems throughout the Unites States presently include a CCS network overlay on the conventional Public Switched Telephone Network (PSTN). The CCS network is preferably implemented utilizing the Signaling System No. 7 (SS7) protocol and is often referred to as the Common Channel Signaling System No. 7 (CCS7) network.
The CCS7 network is a packet switched network that comprises nodes called Signaling Points (SP) and digital links that interconnect the SPs. The SPs are of three basic types; namely, the Signaling Transfer Point (STP), the Service Control Point (SCP), and the Service Switching Point (SSP). The PSTN communicates with the CCS7 network via the SSPs located at the telephone company switching offices such as the end offices and tandem offices. The SSPs are connected to the STPs via digital links and an STP is coupled to an SCP via digital links. The SCPs are databases containing telephone company, subscriber and call related data. The digital links interconnecting the SPs are formed into linksets.
CCS7 separates the signaling function that sets up and supervises a call from the switched voice/data path of the call through the PSTN. Prior to CCS7, the signaling information was carried in-band on the voice/data path.
The CCS7 network conveys data packets called SS7 Signal Units (SU) generated by the SSPs and routed by the STPs. Three types of Signal Units are specified for signaling on the CCS7 network. These are denoted as Message Signal Units (MSU), Link Status Signal Units (LSSU) and Fill-In Signal Units (FISU). CCS7 network links idle by transmitting FISUs. The LSSU conveys link status information between points of the network.
The MSU carries network information and is utilized to convey call set-up and supervision signaling. The MSU also controls transaction oriented functions such as data base queries and responses to the SCPs. An MSU can be of a particular category. For example, an ISUP MSU includes an Integrated Services Digital Network User Part and is generally utilized to transfer call set-up and supervision signaling information. An SCCP MSU includes a Signaling Connection Control Part which provides routing and management functions for transfer of messages other than for call set-up. Query and response MSUs will be of the SCCP category and will include a Transaction Capabilities Application Part (TCAP). An SCCP TCAP MSU will generally be utilized in such transaction oriented functions as queries and responses to SCPs.
An MSU of a particular category can be of a variety of types. For example, an ISUP MSU can be an Initial Address Message (IAM), a Continuity Check Message (COT), an Address Complete Message (ACM), an Answer Message (ANM), or a Release Message (REL).
Other categories of MSUs are the SCCP Unitdata and the SSCP Unitdata Service which have message types of TCAP query, TCAP response, TCAP conversation, and TCAP unidirectional.
The above discussed MSU categories and MSU types within the categories are merely exemplary. Numerous other MSU categories and MSU types are known in the SS7 protocol for performing a variety of functions.
Systems are known in the prior art that couple to the CCS7 network for performing specific dedicated applications. For example, an article in TELECOMMUNICATIONS of July 1987, volume 21 number 7, pages 67-71, entitled "SS7 Testing Tools" by B. Nelson, describes equipment for testing the CCS7 network. The equipment is manufactured by Hewlett-Packard as the Signaling Test Set HP37900D. This equipment can record information at a network point and limited analysis can be performed thereon in an ad hoc fashion.
Another dedicated system is disclosed in U.S. Pat. No. 4,788,718 issued Nov. 29, 1988, entitled "Call Data Collection And Modification Of Received Call Distribution". The disclosed system collects call data from an STP link and processes the call data to perform traffic analysis.
Another such dedicated system is disclosed in U.S. Pat. No. 5,008,929 issued Apr. 16, 1991, entitled "Billing System For Telephone Signaling Network". The system of said U.S. Pat. No. 5,008,929 captures MSUs received by an STP and processes the MSUs to identify, as a service provider, a telephone company that transports an MSU, or a telephone company that provides call data for an MSU, for example, in response to an MSU query. The MSUs are also processed to identify as a recipient for the service, the telephone company that formulated the MSU.
It is appreciated that a telephone company such as an RBOC cannot readily obtain knowledge of the Signal Unit traffic flowing through its CCS network. As discussed, a dedicated system can be designed and deployed to connect to the network to analyze the Signal Unit traffic in accordance with a specifically desired "built-in" application. This approach is wasteful of interface and processing resources, particularly when plural and diverse applications are desired. Analysis of the traffic is done off-line in an ad hoc fashion by the department of the telephone company that desires the traffic data.